In a fight against a phase spider on the Material Plane, would the banishment spell be a viable option to temporarily keep a phase spider out of the fight?
According to the banishment spell, the targeted creature would be banished to a harmless demiplane and incapacitated, if it is native to the Material Plane, but banished to its home plane, if it’s native to a different plane.
Removing the phase spider from combat for up to one minute would be the desired situation. But I do not know the native plane of phase spiders. Banishing it to the Ethereal Plane would yield an unsatisfying result, as it would be able to Ethereal Jaunt right back into the fight.